Certain diseases in which the body becomes unable to extract nutrition from food in the natural manner require the intravenous administration of large daily quantities of hypertonic dextrose in order to keep the patient alive. Continuous long-term administration of dextrose in this manner makes it necessary to hospitalize the patient for extended periods of time and causes health problems such as fatty infiltration of the liver, hyperinsulinism, lipogenesis, and essential fatty acid deficiency, among others.
Most of the foregoing problems can be prevented or treated by administering total parenteral nutrition (TPN) in a cyclic manner in which the infusion of hypertonic dextrose is discontinued each day for a period of eight to twelve hours. In addition to the direct medical benefits of cyclic TPN administration, considerable psychological benefits are gained by allowing the patient free movement for most of the waking day and making it possible for the TPN to be administered in a home environment.
Cyclic TPN has one disadvantage: sudden starting of TPN at the full steady-state infusion rate is prone to cause clinical symptoms of hyperglycemia and rapid electrolyte influx into the cells because of the inability of the pancreas to suddenly adjust to the high glucose load of the TPN volume. Likewise, sudden cessation of TPN without a tapering-off procedure can cause reactive hypoglycemia.
It has been proposed that patients be instructed to use half the maximum infusion rate for an hour or two at the start of each cycle and to do likewise at the end of each cycle. However, this regimen is only a partial solution to the problem, and is also somewhat impractical in a home environment because the patient may be inattentive or asleep at a time when the infusion rate should be changed.